with a mixture of compounds having the formulas RM and RM Where each R is selected from the group consisting of aliphatic, cycloaliphatic and aromatic hydrocarbon radicals having 1 to 20 carbon atoms, M is an alkali metal and x is an integer of 2 to 4, re placing the alkali metal atoms in the resulting polymer With stable reactive groups, and reacting the polymer thus formed with a polyfunctional